Lead-acid batteries date back more than 100 years. Although new secondary batteries such as nickel-metal hydride batteries and lithium-ion batteries have recently been developed, lead-acid batteries are constantly in high demand due to their stability and cost performance. It is still hoped that a lead-acid battery will have a larger capacity and an improved battery life.
Conventionally, in order for a lead-acid battery to have a larger capacity or an improved battery life, usage types of lead-acid batteries have typically been reviewed so as to employ a design suitable for the various types. Since an appropriate design thus tailored to the various usage types of lead-acid batteries requires amendments to the designs of the current collector and of the electrode plates, and review of the battery container design as a whole, a long time and much expense are involved in verifying the designs.
Consequently, in order to increase capacity and improve battery life without any amendment to lead-acid battery designs, methods whereby a chemical is added to a lead-acid battery have been studied. Although various suggestions have been made in the past, most of which are disadvantageous in that they are insufficiently effective or too expensive, only a limited number of the practical applications thereof have been made commercially available. In light of such a situation, there has been a demand for the development of a chemical which can increase the capacity of a lead-acid battery and improve its battery life by a simple method.